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    <script>
        function fn1() {
            console.log(this)
        }

        fn1()

        fn1.call(  { x:100 }  ) // call直接就改变指向执行

        const fn2 = fn1.bind(  { x:200 }  ) // 返回一个新的函数执行，所以需要赋值
        fn2()
    </script>
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